Gas turbine engine and method of assembling same

Abstract

A method of assembling a gas turbine engine that includes rotatably coupling a first low-pressure turbine rotor to a high-pressure turbine, rotatably coupling a second low pressure turbine rotor to the first low-pressure turbine rotor, and rotatably coupling the second low-pressure turbine rotor to a turbine rear-frame such that a weight of the high-pressure turbine is transmitted to the turbine rear-frame.

1. A method of assembling a gas turbine engine, said method comprising:
 rotatably coupling a first low-pressure turbine rotor to a high-pressure turbine using a first differential bearing coupled between the first low-pressure turbine rotor and the high-pressure turbine, wherein the first low-pressure turbine rotor includes a first plurality of turbine blades, each of the first plurality of blades extending radially outwardly from a root end toward a low-pressure turbine casing; 
 rotatably coupling a second low-pressure turbine rotor to the first low-pressure turbine rotor using a second differential bearing coupled between the first low-pressure turbine rotor and the second low-pressure turbine rotor, wherein the second low-pressure turbine rotor includes a second plurality of turbine blades, each of the second plurality of blades extending radially outwardly from a root end toward the low-pressure turbine casing; and 
 rotatably coupling the second low-pressure turbine rotor to a turbine rear-frame such that the weight of the high-pressure turbine is transmitted to the turbine rear-frame. 
 
   
   
     2. A method in accordance with  claim 1  wherein rotatably coupling a second low-pressure turbine rotor to a first low-pressure turbine rotor comprises rotatably coupling a second low-pressure turbine rotor that is rotatable in a first rotational direction to a first low-pressure turbine rotor that is rotatable in a second rotational direction that is opposite that of the first rotational direction. 
   
   
     3. A method in accordance with  claim 2  further comprising coupling a roller bearing between the second low-pressure turbine rotor and the turbine rear-frame. 
   
   
     4. A method in accordance with  claim 1  further comprising channeling oil from the turbine rear frame to the first differential bearing to lubricate the first differential bearing. 
   
   
     5. A method in accordance with  claim 1  wherein rotatably coupling a first low-pressure turbine rotor to a high-pressure turbine comprises coupling a first foil differential bearing between the first low-pressure turbine rotor and the high-pressure turbine such that the high-pressure turbine is rotatably coupled to the first low-pressure turbine rotor. 
   
   
     6. A method in accordance with  claim 1  further comprising coupling the first low-pressure turbine rotor to an aft fan assembly. 
   
   
     7. A method in accordance with  claim 1  further comprising coupling the second low-pressure turbine rotor to a forward fan assembly. 
   
   
     8. A method in accordance with  claim 1  further comprising channeling oil from the turbine rear-frame to at least one of the high-pressure turbine, the first low-pressure turbine rotor, and the second low-pressure turbine rotor. 
   
   
     9. A gas turbine engine comprising:
 a high-pressure turbine; 
 a first low-pressure turbine rotor rotatably coupled to said high-pressure turbine, wherein a first differential bearing is coupled between said first low-pressure turbine rotor and said high-pressure turbine, said first low-pressure turbine rotor comprises a first plurality of turbine blades, each of said first plurality of blades extending radially outwardly from a root end toward a low-pressure turbine easing; 
 a second low-pressure turbine rotor rotatably coupled to said first low-pressure turbine rotor, wherein a second differential bearing is coupled between said first low-pressure turbine rotor and said second low-pressure turbine rotor, said second low-pressure turbine rotor comprises a second plurality of turbine blades, each of said second plurality of blades extending radially outwardly from a root end toward the low-pressure turbine casing; and 
 a turbine rear-frame rotatably coupled to said second low-pressure turbine rotor such that the weight of said high-pressure turbine is transmitted to said turbine rear-frame. 
 
   
   
     10. A gas turbine engine in accordance with  claim 9  wherein said first low-pressure turbine rotor is rotatable in a first rotational direction, and said second low-pressure turbine rotor is rotatable in a second rotational direction that is opposite that of the first rotational direction. 
   
   
     11. A gas turbine engine in accordance with  claim 10  further comprising a roller bearing coupled between said second low-pressure turbine rotor and said turbine rear-frame. 
   
   
     12. A gas turbine engine in accordance with  claim 9  further comprising an oil supply system configured to channel oil from said turbine rear frame to said first differential bearing to lubricate said first differential bearing. 
   
   
     13. A gas turbine engine in accordance with  claim 9  further comprising a first differential foil bearing coupled between said first low-pressure turbine rotor and said high-pressure turbine such that said high-pressure turbine is rotatably coupled to said first low-pressure turbine rotor. 
   
   
     14. A gas turbine engine in accordance with  claim 9  further comprising an aft fan assembly rotatably coupled to said first low-pressure turbine rotor. 
   
   
     15. A gas turbine engine in accordance with  claim 9  further comprising a forward fan assembly rotatably coupled to said second low-pressure turbine rotor, said forward fan assembly configured to rotate in a rotational direction that is different than an aft fan assembly. 
   
   
     16. A gas turbine engine in accordance with  claim 9  further comprising an oil supply system configured to channel oil from said turbine rear-frame to at least one of said high-pressure turbine, said first low-pressure turbine rotor, and said second low-pressure turbine rotor. 
   
   
     17. A method in accordance with  claim 1  further comprising:
 coupling the first low-pressure turbine rotor to a first shaft using a first spline; and 
 coupling the second low-pressure turbine rotor to a second shaft using a second spline. 
 
   
   
     18. A method in accordance with  claim 17  further comprising:
 channeling oil to the first differential bearing via the first spline; and 
 channeling oil to the second differential bearing via the second spline.